Fuel tank for a motor vehicle

ABSTRACT

The invention concerns a fuel tank for a motor vehicle, comprising at least one venting device which is connected to a fuel vapor filter, wherein the venting device includes at least one collecting container for receiving liquid fuel. The fuel tank is distinguished in that disposed within the collecting container is a delivery pump for emptying it into the delivery volume of the fuel tank.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/567,918 filed Dec. 7, 2006, which claims priority to GermanApplication DE 10 2005 058617.1, filed Dec. 7, 2005.

FIELD

The invention concerns a fuel tank for a motor vehicle, comprising atleast one venting device which is connected to a fuel vapor filter,wherein the venting device includes at least one collecting containerfor receiving liquid fuel.

BACKGROUND

A fuel tank of that kind is known for example from EP 1 196 303 B1. Thefuel tank known from EP 1 196 303 includes means for venting same whenrefuelling the tank and in operation of the motor vehicle. The ventinglines are connected in known manner by way of a collecting container toa pressure compensating line connected to an activated carbon filter.

When filling the fuel tank with fuel the gas present in the tank isdisplaced by the incoming flow of liquid. So that no hydrocarbons aredischarged to the atmosphere in the refuelling operation, the gas volumeflow which is displaced in the refuelling operation is usuallydischarged to the atmosphere by way of a fuel vapor filter. The gaseswhich are produced in operation of the motor vehicle as a result ofevaporation of the fuel are also discharged to the atmosphere in acleaned form by way of the fuel vapor filter.

The activated carbon in the fuel vapor filter may not be wetted withliquid hydrocarbons, such wetting would detrimentally affect theadsorptive properties of the activated carbon. For that reason it isknown for collecting containers or beading-out containers to be disposedupstream of the fuel vapor filter in the venting lines. Any condensatewhich is produced as well as entrained liquid hydrocarbon particles aredeposited out in the collecting container and added to the deliveryvolume of the fuel tank again in a suitable fashion.

Collecting containers of that kind are arranged in part outside the fueltank and in part within it.

To avoid potential emission and leakage points, for example EP 1 196 303proposes arranging such a collecting container within the fuel tank sothat it is possible to dispense with the arrangement of lines whichcommunicate the internal space of the fuel tank with the collectingcontainer.

A further advantage of a collecting container which is disposed withinthe fuel tank is that it cannot tear away in the event of the motorvehicle crashing as the collecting container is arranged in a protectedcondition within the fuel tank.

It is readily understandable that the liquid fuel which occurs in thecollecting container or beading-out container must be returned again tothe delivery volume of the fuel tank. That can be easily effected forexample by means of the force of gravity through a drain openingprovided with a valve in the collecting container.

Depending on the respective pressure conditions in the fuel tank anddepending on the respective position of installation of the collectingcontainer, emptying thereof by virtue of the effect of the force ofgravity is not always effectively possible.

Therefore EP 1 196 303 B1 proposes connecting the collecting containerto the suction side of a suction jet pump present in the fuel tank. Thesuction jet pump can be operated for example by the return flow of fuelfrom the engine in operation of the motor vehicle. That effectivelyprovides that the collecting container is sucked out.

Such an arrangement however suffers from the disadvantage thatadditional lines have to be placed within the fuel tank, which meansthat in particular the assembly complication and expenditure incompleting the fuel tank becomes comparatively high.

SUMMARY

Therefore the object of the invention is to develop a fuel tank of thekind set forth in the opening part of this specification in such a waythat effective emptying of the collecting container can be effected withmeans of the utmost simplicity.

That object is attained by the features of claim 1.

Advantageous configurations of the invention are set forth in theappendant claims.

The fuel tank according to the invention is distinguished in thatdisposed within the collecting container is a delivery pump for emptyingit into the delivery volume of the fuel tank. In other words, thedelivery pump for actively emptying the collecting container iscompletely integrated therein so that line connections for connectingsame to a pump arranged outside it are unnecessary. That is advantageousin particular for the reason that mounting installation fitments in thefuel tank can generally only be effected through one or more inspectionopenings, the size of which is such that it is possible to passthereinto with the hand, but it will be noted that in that case theassembly procedure has to be carried out without being able to view it.Accordingly that involves additional complication and expenditure foreach line which is to be laid and clipped in the tank, the suction jetpump or the like. Finally it is necessary for such lines, as alreadyindicated hereinbefore, to be fixed to the tank wall. In that respectthe solution according to the invention represents a substantialsimplification in terms of assembling the fuel tank.

It is particularly desirable if the delivery pump is driven by way of atleast one fan wheel which is so arranged that it can be caused to rotateby the venting flow which is passed through the collecting container. Ina particularly advantageous variant of the fuel tank according to theinvention therefore the drive for the delivery pump is in the form of anaxial turbine which utilises the venting volume flow during refuellingand in operation. In particular so-called ‘on board fuel vapor recovery’systems which are wide-spread on the American market are suitable forthat purpose. In that case the gas volume flow which is produced in therefuelling operation is passed for the major part by way of the fuelvapor filter, and the filling opening of the fuel tank is sealed off inrelation to the refuelling gun during the refuelling procedure.

Desirably, the fan wheel is arranged with a pump impeller of thedelivery pump on a common shaft.

The delivery pump can be for example in the form of a side passage pump.Side passage pumps have the advantage that they are of a particularlycompact size and have few moving parts.

A variant of the fuel tank according to the invention provides that thefan wheel is arranged within a housing having an inner portion and anouter portion, that the inner portion forms a core tube portion whichencloses the fan wheel and that the outer portion forms a casing tubeportion which with the core tube portion forms a suction intake gapwhich narrows in the flow direction of the venting flow.

That arrangement provides that the venting flow which drives the fanwheel is accelerated within the housing or within the suction intake gapso that particularly effective utilisation of the kinetic energy of thegas flow is guaranteed.

Desirably the outer portion is in the form of a bowl which enlarges inthe flow direction and whose bottom has the shaft of the fan wheel andthe pump impeller respectively passing therethrough. The arrangement inthat case is so selected that the gas inlet and the gas outlet from thehousing are arranged on one side thereof.

The delivery pump can be connected for example with its pressure side toan outlet opening of the collecting container, which outlet openingcommunicates with the fuel tank. The outlet opening can be closed with anon-return valve.

In an alternative configuration of the fuel tank according to theinvention the collecting housing comprises two chambers whichcommunicate with each other by way of an overflow opening, wherein afirst chamber is provided as a liquid collecting space and a secondchamber is provided as a gas collecting space, the overflow opening isclosable by a filling level-switched valve and the delivery pump is soconnected that closure of the overflow opening causes a rise in pressurein the liquid collecting space so that emptying thereof occurs by way ofan outlet opening into the delivery volume of the fuel tank. In thisvariant of the configuration of the collecting container the fuel in theliquid collecting space is not conveyed directly by way of the deliverypump, but rather the delivery pump serves only to increase the pressureand thus to provide for indirect emptying of the liquid collecting spacewhen a certain level of liquid is attained therein.

In this embodiment of the invention the delivery pump can be connectedat the suction side to the gas collecting space. The suction side of thepump can alternatively also be connected to the delivery volume of thefuel tank.

Desirably the delivery pump and the drive thereof are combined to formone unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinafter by means of an embodiment by wayof example illustrated in the drawings in which:

FIG. 1 is a diagrammatic view of the fuel tank according to theinvention,

FIG. 2 is a sectional view on an enlarged scale through the collectingcontainer shown in FIG. 1 in accordance with a first embodiment of theinvention, and

FIG. 3 shows a view in section of an alternative configuration of thecollecting container.

DETAILED DESCRIPTION

The fuel tank 1 shown in FIG. 1 includes in known manner a filler pipe 2and means (not shown) for conveying and removing fuel for deliverythereof as well as means for introducing air into and venting the fueltank 1 during refuelling and operation. In general the fuel tank 1 isfor example in the form of a plastic tank which was produced in onepiece by extrusion blow molding. It can be of a comparativelycomplicated, chamber-like structure involving various sub-volumes. Thefuel tank 1 shown in FIG. 1 is illustrated in a greatly simplified formfor the purposes of enhanced clarity.

For the purposes of venting the fuel tank in a refuelling operation orin operation, provided in the fuel tank are various ventilation pointswhich can each be controlled with respective valves. From the valvesventing lines 3 are taken by way of a collecting container 4 to a fuelvapor filter (activated carbon filter) (not shown).

For that purpose the collecting container 4 shown in the Figures isconnected to an operational venting line identified by reference 3 b anda refuelling venting line identified by reference 3 a. Reference 5denotes the pressure compensating line which is passed from the fueltank 1 to an activated carbon filter. Also provided on the collectingcontainer 4 is a drain opening 6 which is closed by a non-return valve7.

The dimensional relationships of the lines 3, 5 shown in FIGS. 2 and 3do not allow any conclusions at all to be drawn about their actualdimensioning in relation to each other. FIGS. 2 and 3 are also highlysimplified diagrammatic views.

Reference is firstly made to FIG. 2 in which the collecting container 4is shown in section on an enlarged scale. Arranged therein is a deliverypump 8 for emptying it, together with an associated drive 9. As will befurther described hereinafter, the drive 9 is in the form of an axialturbine which is driven by way of the venting volume flow or by way ofthe carbon-enriched gas which is passed through the collecting container4 in the venting operation.

The delivery pump 8 is in the form of a side passage pump which is knownper se and whose pump impeller 10 is arranged on a common shaft 12 witha fan wheel 11 which belongs to the drive. The fan wheel 11 in turn isarranged in a two-part housing, wherein the housing includes an outerportion 14 and an inner portion 15. The outer portion 14 forms a casingtube and is of an approximately bowl-shaped configuration and enlargesconically at its side remote from the pump impeller 10. The shaft 12passes through the bottom 16 of the outer portion 14 which forms thefunctional separation between the drive 9 and the pump. The tube-shapedinner portion 15 which encloses the fan wheel 11 is arranged within theouter portion 14 in such a way that a suction intake gap 17 whichnarrows conically in the flow direction is formed between the innerportion 15 and the outer portion 14.

Due to the reduction in cross-section of the suction intake gap 17 thegas flow experiences an acceleration effect. At the bottom 16 of theouter portion 14 the gas flow is finally deflected and passed axiallythrough the inner portion 15 where it causes the fan wheel 11 to bedriven. The fan wheel 11 in turn rotates the shaft 12 and therewith thepump impeller 10. The pump impeller 10, with the pump housing 18, formsa side passage 19 which in known manner is arranged to extend in aspiral configuration and connects an inlet opening 20 (suction side) andan outlet opening 21 (pressure side) of the delivery pump 8.

When refuelling the motor vehicle the gas volume flow which flows inthrough the refuelling venting line 3 a drives the fan wheel 11 andtherewith also the pump impeller 10. The liquid fuel 22 which is onlyillustrated by way of indication is sucked in through the inlet opening20 and pumped through the outlet opening 21 against the non-return valve7 into the delivery volume 23 of the fuel tank 1.

Reference is now made to the embodiment shown in FIG. 3 of thecollecting container 4 which is subdivided by an intermediate wall 24into two chambers, wherein a first chamber is in the form of a liquidcollecting space 25 and a second chamber is in the form of a gascollecting space 26 or a gas inflow chamber.

In the embodiment illustrated in FIG. 3, identical components aredenoted by the same references.

The unit consisting of the delivery pump 8 and the drive 9 passesthrough the intermediate wall 24 of the collecting container 4, with theouter portion 14 being sealed off with respect to the intermediate wall24. Reference 27 denotes a suction intake snorkel which is connected tothe inlet opening 20 of the delivery pump 8 and which also passesthrough the intermediate wall 24 and communicates with the gascollecting space 26. Also provided in the intermediate wall 24 is anoverflow opening 28 by way of which the gas collecting space 26 and theliquid collecting space 25 communicate with each other as long as thelevel of the liquid fuel 22 in the liquid collecting space 25 does notexceed a certain height. The overflow opening 28 is closable by means ofa float valve 29 when a given filling level is exceeded, in which casethe valve body 30 is lifted by the fuel 22 and closes the overflowopening 28.

Particularly in a refuelling operation, the incoming gas volume flowwhich is passed by way of the pressure compensating line 5 to theactivated carbon filter (not shown) drives the fan wheel 11 andtherewith the pump impeller 10 of the delivery pump 8. The delivery pump8 draws gas out of the gas collecting space 26 into the liquidcollecting space 25 by way of the snorkel 27. As the gas collectingspace 26 and the liquid collecting space 25 communicate with each other,the delivery pump 8 is operating virtually in a no-load mode. Thecondensed or beaded-out fuel 22 collects in the liquid collecting space25 until the valve body 30 floats up and closes the overflow opening 28.That causes the delivery pump 8 to produce a pressure rise in the liquidcollecting space 25, which causes emptying of the liquid collectingspace 25 against the closing force of the non-return valve 7. Thenon-return valve 7 is in the form of a flutter valve with an elastomerdisk as the closure body so that the closing force thereof iscomparatively moderate.

LIST OF REFERENCES

-   1 fuel tank-   2 filler pipe-   3 venting lines-   3 a refuelling venting line-   3 b operational venting line-   4 collecting container-   5 pressure compensating line-   6 drain opening-   7 non-return valve-   8 delivery pump-   9 drive-   10 pump impeller-   11 fan wheel-   12 shaft-   13 housing-   14 outer portion-   15 inner portion-   16 bottom of the outer portion-   17 suction intake gap-   18 pump housing-   19 side passage-   20 inlet opening-   21 outlet opening-   22 liquid fuel-   23 delivery volume-   24 intermediate wall-   25 liquid collecting space-   26 gas collecting space-   27 snorkel-   28 overflow opening-   29 float valve-   30 valve body

1. A fuel tank for a motor vehicle, comprising at least one ventingdevice which is connected to a fuel vapor filter, wherein the ventingdevice includes at least one collecting container for receiving liquidfuel, characterised in that disposed within the collecting container isa delivery pump for emptying it into the delivery volume of the fueltank, characterised in that the delivery pump is driven by way of atleast one fan wheel which is so arranged that it can be caused to rotateby the venting flow which is passed through the collecting container. 2.A fuel tank as set forth in claim 1 characterised in that the fan wheelis arranged with a pump impeller of the delivery pump on a common shaft.3. A fuel tank as set forth in claim 1 characterised in that thedelivery pump is in the form of a side passage pump.
 4. A fuel tank asset forth in claim 1 characterised in that the fan wheel is arrangedwithin a housing having an inner portion and an outer portion, that theinner portion forms a core tube portion which encloses the fan wheel andthat the outer portion forms a casing tube portion which with the coretube portion forms a suction intake gap which narrows in the flowdirection of the venting flow.
 5. A fuel tank as set forth in claim 4characterised in that the outer portion is in the form of a bowl whichenlarges conically in the flow direction and whose bottom has the shaftof the fan wheel and the pump impeller respectively passingtherethrough.
 6. A fuel tank as set forth in claim 1 characterised inthat the delivery pump is connected with its pressure side to an outletopening of the collecting container, which outlet opening communicateswith the fuel tank.
 7. A fuel tank as set forth in claim 1 characterisedin that the collecting housing comprises two chambers which communicatewith each other by way of an overflow opening, that a first chamber isprovided as a liquid collecting space and a second chamber is providedas a gas collecting space, the overflow opening is closable by a fillinglevel-switched valve and the delivery pump is so connected that closureof the overflow opening causes a rise in pressure in the liquidcollecting space so that emptying thereof occurs by way of an outletopening into the delivery volume of the fuel tank.
 8. A fuel tank as setforth in claim 7 characterised in that the delivery pump is connected atthe suction side to the gas collecting space.
 9. A fuel tank as setforth in claim 1 characterised in that the delivery pump and a drivethereof are combined to form one unit.